Door operators and door closers employ mechanical devices to replace the human effort of pushing or pulling a door. Automated doors make entrances accessible to disabled users as well as increase the convenience for all users.
Door closers are used to automatically close doors that have been manually opened. Door operators are similar to door closers but are able to both open and close doors automatically. A common door operator design combines a motor with a door closer and uses the motor to open the door and a spring to close the door. A powerful motor is typically required to overcome the force of the spring. An alternative door operator design eliminates the spring and uses a reversible motor to both open and close the door.
Door operators and door closers must comply with various local and national building codes and regulations. Local regulations may include state building codes or fire codes and may include more stringent regulations from other states, particularly California. National regulations may include building accessibility regulations required by the Americans with Disabilities Act (ADA). Doors typically must comply with force limits for actions such as opening a door, unlatching a door, setting a door in motion and swinging a door to a fully open position. For instance, a door is considered ADA-compliant when the force for opening the door does not exceed 5 pounds. The same actions may have different standards under different codes and regulations. For example, a state fire code may specify that a door unlatch when subjected to a 15 pound force, the door be set in motion when subjected to a 30 pound force and the door swing to a fully open position when subjected to a 15 pound force. The California fire code may be more stringent and may specify that a door unlatch when subjected to a 15 pound force, the door be set in motion when subjected to a 15 pound force and the door swing to a fully open position when subjected to a 15 pound force. ADA regulations may be even more stringent and may require that a door unlatch when subjected to a 5 pound force, the door be set in motion when subjected to a 5 pound force and the door swing to a fully open position when subjected to a 5 pound force.
Door operators and door closers typically include a series of gears to provide a mechanical advantage when opening or closing a door and comply with the force limits set by local and national building codes and regulations. A gear assembly may increase the output of a motor or aid in the compression or stretching of a spring to produce a more efficient door operator or door closer. Gear assemblies are often complex and include multiple gears to achieve a desired mechanical output. Including multiple gears in a gear assembly complicates the manufacturing process and increases costs. The presence of multiple gears and other mechanical components within a door operator or closer also increases the possibility of mechanical failure. There is a need for a gear assembly that is compact and uses a minimal number of gears to produce the necessary mechanical advantage required for use in a door operator or door closer.